1. Field of the Invention
The present invention relates to a vibration driven motor, and, more particularly, to a vibration driven motor of a type arranged in such a manner that an elastic member for generating a travelling vibration wave is moved along a rail-like stator.
2. Related Background Art
Hitherto, there has been disclosed a structure of a vibration driven motor of the type described above, for example, constituted as shown in FIGS. 6 and 7.
Referring to the drawings, reference numeral 1 represents an elastic member in the form of an ellipse and having a projection 1a formed on the moving side thereof, a piezo-electric element 2 bonded to the elastic member 1 on the top surface thereof for the purpose of generating a travelling vibration wave. Reference numeral 8 represents a rail-like stator for frictionally coming in contact with the elastic member 1, the rail-like stator 8 being brought into press-contact with an elastic spring 3 via a vibration insulating material 5 (for example felt).
Reference numeral 6 represents a comb shaped stopper having a comb portion 6a inserted into a slit formed in the portion of the elastic member 1 which is not positioned in contact with the rail-like stator 8. The comb portion 6a supports the elastic member 1 via a felt 7 placed in the bottom portion of the slit.
The elastic member 1 is supported on a frame 4 via the stopper 6 and the elastic spring 3. The frame 4, to which a printing head (omitted from illustration) is fixed is supported by a restricting member 9 for restricting the displacement except for that in direction By which is the predetermined direction of movement.
When the travelling vibration wave is formed in the elastic member 1 by a known method, the elastic member 1 moves on the rail-like stator 8 due to the frictional force generated by the rail-like stator 8 and the elastic member 1. In accordance with this, the frame 4 and the other elements 3, 5, 6 and 7 move in the direction BY along the restricting member 9. The frictional driving force generated at this time acts on a portion of the elastic member 1. Since the frictional driving force does not act on the supporting portion of the elastic member 1, a moment is generated in the elastic member 1, causing the elastic member 1 to be shifted in directions BX and BY.
The comb portion 6a of the stopper 6 is, as shown in FIG. 7, inserted into the slit portion (omitted from illustration) formed in the elastic member 1. As a result, the displacement of the elastic member 1 in the direction By is restricted and the dead weight of the elastic member 1 is supported by the comb portion 6a via the felt 7. Restricting portions 6b and 6c restrict the displacement of the elastic member 1 in the direction Bx, while a restricting member 6d restricts the displacement of the elastic member 1 in the direction By on the side to which the pressure is applied. As a result of the actions of the restricting members 6a to 6d, shake of the elastic member 1 can be prevented so that it can be moved smoothly and linearly together with the frame 4.
However, according to the above-described conventional structure, since the bottom surface of the rail-like stator 8 is positioned in full contact with the bottom plate 10, the stator 8 cannot with completely contact with the bottom plate 10 if the accuracy of the flatness of the bottom surface is insufficient, causing a partial gap to be generated. As a result, the rail-like stator 8 and the bottom plate 10 undesirably beat each other due to the movement of the elastic member 1, causing noise to be generated.
An object of the present invention is to provide a vibration driving motor which is capable of overcoming the above-described conventional problem and in which the rail-like stator can be reliably secured to the bottom plate by a simple structure.
Other and further objects, features and advantages of the invention will be appear more fully from the following description.